Could a self healing concrete be on the way?
A fungi which could help repair cracks in ageing concrete is being developed in America. Researchers at Binghamton University, New York, are developing the organism which could offer a low cost, sustainable and pollution free solution to maintaining and fixing concrete.
Congrui Jin is the assistant professor of mechanical engineering at Binghamton University. She’s found the problems with concrete often start with the smallest of cracks. "Without proper treatment, cracks tend to progress further and eventually require costly repair," she says.
"If micro-cracks expand and reach the steel reinforcement, not only the concrete will be attacked, but also the reinforcement will be corroded, as it is exposed to water, oxygen, possibly CO2 and chlorides, leading to structural failure."
Jin and her team wanted to find out if there was a way of fixing the concrete permanently. "This idea was originally inspired by the miraculous ability of the human body to heal itself of cuts, bruises and broken bones," says Jin. "For the damaged skins and tissues, the host will take in nutrients that can produce new substitutes to heal the damaged parts."
Jin's team, which includes NIng Zhang from Rutgers University, began work on a solution, finding an answer in an unlikely place. They discovered a fungus called Trichoderma Reesei when mixed with concrete is dormant - until cracks start forming. "The fungal spores, together with nutrients, will be placed into the concrete matrix during the mixing process. When cracking occurs, water and oxygen will find their way in. With enough water and oxygen, the dormant fungal spores will germinate, grow and precipitate calcium carbonate to heal the cracks," explains Jin.
"When the cracks are completely filled and ultimately no more water or oxygen can enter inside, the fungi will again form spores. As the environmental conditions become favourable in later stages, the spores could be wakened again."
One of the biggest challenges is enabling the fungus to survive in the harsh environment found within concrete but the development team is hopeful.
"There are still significant challenges to bring an efficient self-healing product to the concrete market. In my opinion, further investigation in alternative microorganisms such as fungi and yeasts for the application of self-healing concrete becomes of great potential importance," says Jin.
New Zealand’s biggest concrete supplier, Firth, is interested in the development. The company says it’s looking forward to seeing if it can be developed for commercial use. A company spokesperson says replacing a biological process rather than the existing proprietary products that work by chemical process would fit very nicely in with the company's Declare Labels.
See more on the development here